This invention describes a method for mapping of a high resolution digital image into a lower resolution frame, and more specifically describes a method of mapping handwritten scripts in the form of high resolution digital data into a lower resolution frame such as a Liquid Crystal Display (LCD).
As used herein, the term "mapping" refers to the process of selection of the appropriate pixels in the lower resolution display in order to form a visual image of a higher resolution digital image on the display device, and does not include any offset or skewing correction between the high resolution and the lower resolution frames. The offset and skewing errors can be corrected as described in U.S. patent application Ser. No. 640,321 U.S. Pat. No. 5,115,107, filed Jan. 11, 1991, inventor John F. Crooks et al, titled "Method of Correcting Skew Between a Digitizer and a Digital Design", and commonly assigned with the present application. Said application is incorporated herein by reference.
In many systems such as PC notebooks and signature capture and verification devices, typically handwritten scripts are electronically captured and visually displayed on a panel such as an LCD. An example of such a system may be seen in U.S. patent application Ser. No. 575,096 filed Aug. 30, 1990, and commonly assigned with the present application. Said application is incorporated herein by reference. In that system, an LCD module which is operatively connected to a microprocessor is placed directly behind a transparent digitizer, which is operatively behind a transparent digitizer, which is operatively connected to the microprocessor whereby positional and script inputs are captured via a stylus operatively connected to the digitizer. As the stylus is used to input script information, the LCD module is driven by the microprocessor to display the image traced by the stylus.
The visual quality of the traced image displayed on the display device is primarily determined by the resolution of the digitizer, the resolution of the display device, and the sampling rate of the digitizer. Typically, the resolution of the digitizer (approximately 500 dots/inch) is much higher than the resolution of the display device (approximately 75 dots/inch) because of the higher costs of the higher resolution displays and the memory elements required for the operation thereof. Thus, the visual quality of the image traced by the stylus and displayed on the display device is essentially determined by the resolution of the display device.
In such systems, where the display device has a lower resolution than the digitizer, in order to display a visual image of a pattern traced by the stylus tip, the samples obtained by the digitizer which are in the form of a high resolution digital data must be mapped into the display grid. In prior art techniques, the higher resolution digitizer data is first truncated or rounded off to the resolution of the display device, and thereafter a visual image is formed by the activation of those display pixels corresponding to the truncated or rounded off data and the graphical connection of those display pixels representing lines. However, such techniques do not always yield the best visual image of the pattern being presented by the display device, more particularly in the cases where the high resolution digital samples of the traced pattern are closely spaced on the display grid. The poorer visual quality of the displayed pattern is mainly caused by the ineffective selection of display device pixels corresponding to the digital image and the poor method of the graphical connection of those pixels forming a line.